What's the difference between isset() and array_key_exists() ?

Here is the difference between isset() and array_key_exists() in PHP:

isset()

• isset() checks if a variable is set and is not NULL.
• For arrays, isset() checks if the specified key exists and has a non-NULL value.
• If the key exists but its value is NULL, isset() will return false.
• isset() can check multiple variables/array keys at once, returning true only if all of them are set.

array_key_exists()

• array_key_exists() checks if the specified key exists in the given array, regardless of its value.
• It returns true if the key exists, even if its value is NULL.
• array_key_exists() can only check one array key at a time.

In summary:

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